For the IP-layer security of router networks, proposed protocols*3 each require a pair of unique encryption and decryption keys for a respective IP datagram.
A solution for the requirement may be such an automatic key generation system that derives a series of pairs of session keys from an original keying material. A respective derived pair is employable to generate a sequence of pairs of encryption and decryption keys for an extensive use of the original keying material, with a problem that a compromised secrecy of a session key permits an access to past, used keys and future, yet unused keys.
An IPSEC (Internet Protocol Security) Working Group of the IETF (International Engineering Task Force) has drafted an ISAKMP (Internet Security Association and Key Management Protocol)*4 as a framework for key management to support a current IPSEC protocol and a subsequent IPv6 (Internet Protocol version 6), and an Oakley*5 as a set of key determination protocols for current use, with a postponed solution to the problem.
The ISAKMP and Oakley support the perfect forward secrecy to a practical extent.
However, in the IP-layer with a mechanism to a standard default algorithm DES(Data Encryption Standard)-CBC(Cipher Block Chaining), a conforming session key has a reduced security due to cookies transmitted on a net, and a resultant short-term security service calls for a frequent Diffie-Hellman key exchange to an extent that causes a fairly high traffic overhead via out-of-band mechanisms. The performance subjected to high overhead and the security of session keys have a trade-off relationship to each other.